The ribonucleotide reductase enzyme of herpes simplex virus consists of 2 components which must remain associated for the enzyme to convert ribonucleotide diphosphates to deoxy ribonucleotide diphosphates. The enzyme is known to be required for herpes simplex virus replication. Dutia et al., Nature 321:439-441 (1986) and Cohen et al., Nature 321:441-443 (1986) both disclosed that the nonapeptide, Tyr Ala Gly Ala Val Val Asn Asp Leu, inhibited in vitro the activity of this enzyme. In addition Dutia et al., op. cit., also disclosed that its 8-desalanine homolog, Tyr Gly Ala Val Val Asn Asp Leu, also inhibited in vitro the activity of this enzyme.